Spark-plug.



F. W. GEAR.

SPARK much. APPLICATION FILED MAR. 28. 1916.

Patnted Apr. 23,1918.

A TTOR/VEYJ.

FREDERICK W. GEAR, OF NEW YORK, N. Y.

SPARK-PLUG.

Specification ol Letters Patent.

Patented Apr. 23, 1916.

Application filed March 28, 1916. Serial No. 87,181.

To all whom it may concern:

Be it known that I, FREDERICK W. GEAR, a subject of the King of Great Britain, and aresident of the borough of Manhattan, in the city, county,'and State of New York,

have invented certain new and useful Im' provements in Spark-Plugs, of which the following is a specification.

One object of this invention is to provide a spark plug with an auxiliary tell-tale spark gap which raises the voltage at the main gap and thereby increases the efficacy of the ignition spark, and also indicates to the eye whether the plug is performing or not. It has been heretofore proposed. to provide spark plugs with such auxiliary gaps, but in order to render them Visible and still to avoid risk of igniting explosive vapors about the engine, they have been housed within impervious transparent walls. In such constructions, the auxiliary gap is surrounded by a body of trapped air which becomes heated and altered by the continued passing of the auxiliary spark therein, with the result that the resistance is varied and the action of the plug rendered unreliable. Furthermore, the' materials used, glass, mica, etc., are breakable and give rise to danger of serious explosions. I overcome these difliculties and make the tell-talespark gap safe and practicable by disposing it in an open chamber which is guarded by a gauze or screen; the screen permitting the air at the gap to be renewed and retaining.

the advantage of visibility while preventing all' outward propagation of flame. In this way the performance .of the plug is made uniform and safety is insured. The invention accordingly comprises a spark plug having a gauze-guarded tell-tale spark gap, and also certain preferred constructional features in relation thereto.

In the accompanying drawings illustrating the preferred embodiment of the plug:

Figure 1 is an elevation;

Fig. 2 is a longitudinal section;

Fig. 3 is a view looking at the inner end of the plug; and i Fig. 4 is a cross-section on the lined-4; of Fig. 2. I The structural part of the shell, as preferably embodied, includes an inner shell 1 and an outer shell 2. The inner shell is screwed into the cylinder wall in the usual manner, being thereby included in the sparking circuit, which is grounded on the engine as well understood. The outer shell,

so termed because it is located outside the engine cylinder, is screwed intothe inner shell, as shown at 4:. The two shells inclose a cavity wherein is held a core 5, of suitable insulating material, having an enlargement 6, which is held between opposed shoulders 7 and 8 0n the two shells, respectively.

Compressible washers 9 and 9 are interposed between the shoulders and the enlargement to prevent injury to the core when the outer shell is screwed home, and to secure tight joints.

Through this core passes a conductor rod section 10, the inner end of which constitutes one of the terminals of the main or ignition spark gap. The other terminal, in the particular instance illustrated, is formed by the edge ofa restricted central opening 11 in an end wall 12 of the inner shell, which. end wall separates a chamber 13 from the combustion space of the engine cylinder.

The outer portion of the said rod section bears a nut 14:, which clamps the rod in place in the core, and is extended beyondthis nut into a chamber 15 in the outer part of the plug, that is to say the portion of the plug which is external to the engine cyl nder. Preferably this chamber is formed in a into the outer shell 2,.the said core and shell second insulating core 16, which is inserted being provided with lateral openings 1? which register when the device is assembled, as seen in .Figs. 2 and 4. These openings are for sight and ventilation, and are guarded by a tubular wire gauze 18. which is pref erably slipped onto a reduced portion 19 of the core, so as to be firmly supportedand held laterally between the core and shell, which also prevent endwise displacement of the gauze by means of shoulders 20 and 21. I

The said chamber incloses the auxiliary spark gap, which is formed by the spaced ends of the rod section 10 and a second rod section 22 passing through the outer end of the core 16. Adjustmentof this spark gap is preferably provided for by making the rod 22 in the form of a screw having-a suitable electrode tip 23, the threads of the screw engaging internal threads formed in the axial opening through the outer part of the said core 16.

A cap .24, of insulating material takes over the end of the outer.

shell 2 and has a vplain central aperture through which the screw passes loosely. "A

nut 25 on the outer portion of the screw is with an outward facing shoulder 26 which abuts against the internal shoulder 21; in the shel1 2, so that when the said nut is screwed forcibly up against the cap 24, not only is the latter held in place but the said core and shell are also drawn together, and

. in thisway, further, the gauze is locked in place. Manifestly, however, these details of construction, While desirable, may be considerably varied. Another nut 27 on the screw serves to bind the terminal of the external conductor to the central conductor of the plug.

The important functions of the open chamber 16 and the gauze in connection with the auxiliary spark gap have already been explained, and the operation thereof will be readily understood.

The chamber 13 heretofore mentioned keeps the main terminals free of carbon deposits, because of the dislodging effect of the explosion of gas pocketed therein. .Ad ditional small openings 28 are shown in the Wall of this chamber at oppgsite sides'of the central opening, in order to insure the admission thereto of a portion of the sev eral explosive charges compressed in the engine cylinder preparatory t'q firing.

While I have illustrated aifd described one embodiment of my inven ion, it will be understood that numerous ot ier and different 'embodimlents may be constructed containing the same essentials, and that I do not limit myself to the precise details herein set forth. I

What I claim as new is:

1. A 'fspark plug, comprising inner and outer shells screwed together, an inner core of insulating material within the inner shell, an electrode rod passing through said inner core, an outer core of insulating material within the outer shell, said core having a chambered reduced portion leaving an annular space between the same and the encircling inner surface of the outer shell, said reduced portion and the outer shell having lateral openings for sight and ventilation, a tubular gauze slipped onto said reduced portion and confined within said annular space, and a second electrode rod passing through the outer part of the outer core and terminating in the chamber thereof at a distance from the outer end of the other rod.

2. A spark plug, comprising inner and outer shells screwed together, an inner core of insulating material within the inner shell, an electrode rod passing through said inner core, an outer core of insulating material within the outer shell, said core having "a I chambered reduced portion leaving an annular space between the same and the encircling inner surface of the outer shell, said reduced portion and the outer shell having lateltal openings for sight and ventilation, a tubular gauze slipped onto said reduced portion and confined within said annular space, a second electrode rod passing through the outer part of the outer core and terminating in the chamber thereof at a distance from the outer end of the other rod, the outer shell and outer core having abutting shoul-' ders, a cap of insulating material covering the outer end of the outer shell, and a nut on the outer rod outside of the cap and cooperative with said rod to draw the outer core against the shoulder of the outer shell and to clamp said shell and core and the cap together.

FREDERICK W. GEAR. 

